BLOOD PARASITES IN BRIGHT BIRDS - TESTING THE HAMILTON-ZUK HYPOTHESISIN SUB-SAHARAN AFRICA WITH AN IMPROVED STATISTICAL-METHOD

The data contained in a catalogue of avian haematozoa for sub-Saharan Africa were examined in the light of the Hamilton-Zuk hypothesis. The males of 464 passerine species were assigned six brightness scores. Ti le generalized linear model with a binomial distribution and logistic link function is shown to be the appropriate statistical tool for anal ysing blood parasite data. With caveats, results from the model suppor ted the prediction that bright males tend to be parasitized more frequ ently. However, the group of species with the highest brightness score , had infection rates similar to the dullest group. When phylogenetic associations were taken into account, support for the Hamilton-Zuk hyp othesis was equivocal. Further research on the ecology and natural his tory of the interactions between blood parasites, their vectors and th e birds they infest is needed to decide whether the differences betwee n the lowest and highest infestation rates (23% for the dullest specie s and 37% for the penultimate brightness score) are biologically meani ngful.